1. Field of the Invention
The present invention relates to an active energy ray-curable inkjet ink, an ink container, and an inkjet discharging device.
2. Description of the Related Art
In recent years, studies have been made for replacing water-based and solvent-based inkjet inks with active energy ray-curable inkjet inks having relatively low volatility.
Recently, there have been increasing demands for the active energy ray-curable inkjet inks to be inkjet-printable onto also a base material that is subjected to stretching, punching, etc. later.
However, a cured film of a conventional active energy ray-curable inkjet ink containing a monofunctional photopolymerizable compound and a multifunctional photopolymerizable compound has a high coated film hardness. Therefore, in the stretching or punching performed after the printing, there occurs a problem that the cured film cannot conform to the deformation of the base material, and that stretchability and punchability of the printed product are poor. Furthermore, because the active energy ray-curable inkjet inks are greatly inferior to the conventional solvent-based inks, expected replacement has not yet advanced drastically up until now, particularly in high-quality applications where molding is required.
For example, there is proposed an ink composition that contains: a photopolymerization initiator; and as a photopolymerizable compound, a specific amount of a photopolymerizable monomer containing one ethylenic unsaturated double bond and at least one urethane bond, and that has favorable stretchability and close adhesiveness (see Japanese Patent Application Laid-Open (JP-A) No. 2012-7107).
There is also proposed a curable composition for surface protection that contains polyester-based urethane (meth)acrylate having a weight average molecular weight of 500 or greater (see JP-A No. 2012-67314).
There is also proposed an irradiation-curable inkjet ink that contains: a unifunctional monomer substance having one irradiation-polymerizable unsaturated carbon-carbon bond; a multifunctional monomer substance having a plurality of irradiation-polymerizable unsaturated carbon-carbon bonds; and an oligomer having at least one irradiation-polymerizable unsaturated carbon-carbon bond (see Japanese Patent (JP-B) No. 3619778).
There is also proposed an ultraviolet-curable ink that contains a reactive oligomer having a glass transition temperature (Tg) of from −25° C. to 70° C., or a reactive prepolymer having a glass transition temperature (Tg) of from −25° C. to 70° C., or both thereof, that has a specific viscosity and a specific flexibility, and that is excellent in scratch resistance and adhesiveness (see JP-B No. 4754779).
There is also proposed an active energy ray-curable inkjet ink that contains as polymerizable monomers, a specific monofunctional monomer and a specific multifunctional monomer, wherein a cured film of the ink has a mass change ratio of 30% by mass or lower after immersed in the ink for 30 seconds, and a cured film of the ink has a cure shrinkage ratio of 5% or lower (see JP-B No. 4899430).